1. Field of the Invention
The present invention is generally related to an exhaust valve actuator and, more particularly, to an exhaust valve actuator that incorporates an air compressor to provide air pressure that is used to actuate an exhaust valve under the control of an engine control module.
2. Description of the Prior Art
Exhaust valves used in conjunction with two cycle engines are well known to those skilled in the art.
U.S. Pat. No. 4,539,813, which issued to Tomita et al on Sep. 10, 1985, describes an exhaust system control apparatus in an internal combustion engine. The exhaust system includes a subsidiary chamber connected to the normal exhaust passage with a valve for opening and closing communication between the chamber and exhaust passage to change the pressure wave at the engine cylinder exhaust port to provide optimum performance at high and low speeds. The chamber valve is operated rapidly by a pneumatic actuator supplied with compressed air from one or more of the sources disclosed, namely, a belt driven or electric air compressor and piston and a cylinder device extending between or forming the suspension components of a two wheeled vehicle. A pneumatic valve is operated by engine speed sensing means to supply or release the pressurized air to the actuator at a predetermined engine speed.
U.S. Pat. No. 5,873,334, which issued to Heinrich on Feb. 23, 1999, describes an exhaust valve system for a two cycle engine. The engine includes a cylinder having an exhaust port with an axial extent along the axis of the cylinder structure. An exhaust port valve is mounted adjacent to the exhaust port and is adjustable between a full flow position, in which the exhaust port valve exposes the exhaust port throughout its axial extent, and a restricting position, in which the exhaust port valve restricts the axial extent of the exhaust port. A valve control module is connected to the exhaust port valve and functions to adjust the exhaust port valve between the full flow and restricting positions in response to the cylinder bore gas pressure. At low speeds and low output conditions, the valve is in its restricting position. As the cylinder develops higher pressures at higher speeds and under higher output conditions, the valve control module moves the valve to its full flow position.
U.S. Pat. No. 4,986,780, which issued to Sougawa on Jan. 22, 1991, describes a two cycle engine and several embodiments of outboard motors embodying two cycle internal combustion engines which have an exhaust control valve and a decompression control valve that is operated in response to engine operating characteristics to improve performance and to reduce noise. Embodiments are disclosed wherein the control is in response to throttle valve position, engine speed and/or exhaust gas pressure.
U.S. Pat. No. 4,829,946, which issued to Boyesen on May 16, 1989, describes an exhaust control valve for a two cycle engine and a process for using the same. The control valve is located within the exhaust passage, seals against the piston, and delays opening of the exhaust passage to the combustion chamber during the expansion stroke of the piston for a preselected number of degrees of rotation of the crankshaft while permitting full opening of the exhaust port during the scavenging cycle. Also disclosed are means for modifying opening of the exhaust valve at high engine speeds to improve scavenging.
U.S. Pat. No. 4,723, 514, which issued to Taniuchi on Feb. 9, 1988, describes an exhaust timing control system for a two cycle engine. The system incorporates a pivotally mounted control valve to selectively close the upper portion of an exhaust port in a two cycle engine including a motor coupled with the valve for driving the same. A speed determination means is provided to determine the engine speed relative to a specified value. A drive means rotates the motor in either direction based on the sensing by the speed determination means. A drive current control means detects the magnitude of change of the engine speed and increases or decreases the current supplied to the motor to increase or decrease the speed of change of the control valve.
U.S. Pat. No. 4,391,234, which issued to Holzleitner on Jul. 5, 1983, describes an internal combustion engine comprising means for controlling the axial extent of a port in a cylinder. In an engine comprising at least one cylinder having a port and a piston which is reciprocal to open and close the port, the effective axial extent of said port is adapted to be reduced by a restricting member which is movably mounted adjacent to a flow passage which adjoins the port. The restricting member has a restricting edge and is movable to a restricting position in which the restricting edge is substantially flush with the peripheral surface of the cylinder bore. The restricting member defines the exhaust passage on one side thereof adjacent to the exhaust port. In order to improve the cooling of the cylinder and the exhaust gas flow, the restricting member constitutes a hinged member which is pivoted on an axis at that end which is opposite to the restricting edge.
U.S. Pat. No. 4,388,894, which issued to Tanaka et al on Jun. 21, 1983, describes a two stroke engine having exhaust timing control valve means. The two stroke has an exhaust port formed in the cylinder wall. At the upper portion of the exhaust port, there is provided a rotary type exhaust timing control valve which is adapted to be actuated by an electric servo motor to control the exhaust timing in accordance with the engine speed. A control circuit is provided for controlling for a power supply to the servo motor in accordance with the engine speed and the position of the valve. A timer switch is provided for providing a power supply to the control circuit for a certain time after the engine ignition switch is turned off so that the valve is moved to the retracted position after the engine is stopped. As the valve is thus moved to the retracted position, carbon deposits on the valve are scraped off by a scraping edge formed in the cylinder.
U.S. Pat. No. 4,364,346, which issued to Shiohara on Dec. 21, 1982, describes an exhaust timing device for a two cycle engine. The device, in which a valve member functioning as the upper edge of an exhaust port that opens into the inner circumference of a cylinder is disposed in the upper wall of the exhaust passage from the exhaust port. A valve hole having an elongated cross section is opened in the wall of the exhaust passage in the vicinity of the exhaust port and is formed at the inclination with respect to the axis of the cylinder. The valve member is arranged slidably in the valve hole to that it can be retracted into the valve hole until the leading end portion thereof becomes substantially coextensive with the inner wall surface of the exhaust passage.
U.S. Pat. No. 4,341,188, which issued to Nerstrom on Jul. 27, 1982, describes a two cycle internal combustion engine which includes means for varying cylinder port timing. The engine includes an engine block having a cylindrical wall defining a cylinder having a head end, a piston mounted for reciprocative movement in the cylinder, and a passage in the engine block, such as an exhaust passage, a transfer passage, or a crankcase fuel intake passage, terminating at the cylinder wall in a port, such as an exhaust port, a transfer port, or a piston controlled, crankcase fuel intake port, having upper and lower edges. A valve mounted in the passage for movement relative to the port is operable to selectively vary the effective distance of one of the port edges from the cylinder head end and thereby provide the capability of varying the timing of the port opening and/or closing as required to obtain optimum engine performance at different operating conditions.
U.S. Pat. No. 4,399,788, which issued to Bostelmann on Aug. 23, 1983, described an internal combustion engine comprising means for controlling the axial extent of an exhaust port in a cylinder. In a two stroke cycle internal combustion engine, cylinder structure has an inside peripheral surface which defines a cylinder bore and is formed with an exhaust port, which has an axial extent along the axis of said cylinder bore and communicates with said exhaust system. A piston is axially reciprocal in said cylinder bore and adapted to open and close said port. A restricting member is mounted in said cylinder structure adjacent to said port and adjustable between a full flow position, in which said restricting member exposes said exhaust port throughout its axial extent, and a restricting position, in which said restricting member restricts the axial extent of said exhaust port. A positioning drive is operatively connected to said restricting member and operable to adjust said restricting member between said full flow and restricting positions. The positioning drive is adapted to be controlled in dependence on the exhaust gas pressure in said exhaust gas system.
The above United States patent are hereby explicitly incorporated by reference in the description of the present invention.
Exhaust valves are typically provided to allow an engine to operate more efficiently and effectively at low operating speeds even though they are generally tuned for operation at higher speed ranges. When an engine is tuned for its best operation at higher speeds, low speed power is often compromised. This is particularly true for fixed geometry exhaust systems which are commonly used in outboard motor applications. As a result, acceleration performance at lower engine speeds is often less than desired. By providing an exhaust valve, certain advantages can be achieved. For example, exhaust emissions of unburned hydrocarbons can be minimized if the exhaust port size is reduced when the engine is operating at low speeds. Furthermore, the gas dynamic behavior of exhaust systems typically exhibit an expansion wave and a compression wave which arrive at the exhaust port at certain times during each cycle of the engine. By selectively altering the effective cross sectional area of the exhaust conduit of an engine, these expansion and compression waves can be used advantageously instead of occurring deleteriously. These and other advantages of exhaust valves are well known to those skilled in the art.
Exhaust valves known in the prior art are typically actuated by exhaust pressure, cylinder pressure, or by stepper motors. The use of exhaust pressure is generally undesirable since it can be affected by outboard motor installation and by boat operating conditions. Cylinder pressure activation is undesirable in many cases because the cylinder pressure can be affected by cylinder combustion quality. The use of a stepper motor is usually prohibitally expensive, especially when it is considered that many engines have multiple cylinders and each cylinder may require an individual stepper motor for these purposes.
It would therefore be significantly beneficial if a means for actuating an exhaust valve could be provided without the disadvantages incumbent with exhaust pressure actuation, cylinder pressure actuation, and stepper motor actuation.
An exhaust valve control system for an internal combustion engine, principally an outboard motor engine, made in accordance with the present invention comprises a compressor, a controller, an exhaust valve associated with the exhaust conduit of a cylinder of the engine, and a pressure valve. The pressure valve is connected in signal communication with the controller, which can be an engine control module or engine control unit, and is connected in fluid communication with the compressor. The compressor provides actuating pressure for the exhaust valve and this pressure is ported to the exhaust valve through the pressure valve. The controller determines the position of the exhaust valve relative to the exhaust conduit by controlling the pressure valve as a function of at least one operating parameter of the internal combustion engine. The exhaust valve is disposed within the exhaust conduit of a cylinder of the engine and within the exhaust flow stream emanating from the exhaust port of the cylinder and flowing through the exhaust system.
The exhaust valve can be a two position valve in which a first position completely opens the exhaust conduit and a second position completely closes the exhaust conduit. Alternatively, the exhaust valve can be movable to any one of a plurality of positions between fully closed and fully opened.
The exhaust valve control system of the present invention can further comprise an air rail connected in fluid communication with a compressor and a pressure regulator connected in fluid communication with the air rail to maintain a preselected pressure within the air rail. The system can further comprise an engine speed sensor connected in signal communication with the controller, wherein the controller determines the position of the exhaust valve relative to the exhaust conduit by controlling the pressure valve as a function of an engine speed signal received by the controller from the engine speed sensor. Alternatively, the system can comprise an engine load sensor in which the controller controls the position of the exhaust valve as a function of an engine load signal received from the engine load sensor.
The pneumatic circuit of the present invention can further comprise a pressure accumulator connected in fluid communication with the air compressor and, in certain embodiments, between the air compressor and the air rail.